I see it being pretty even considering each others backgrounds. I'ma have to go with Cain o this one though just for the fact that he improves a lot after each fight & Lesnar has been out of action for a while now.
Not knockin Brock or anything ... but his chin has yet to be tested... couture caught him with a few shots... and he admitted he saw "tweety bird" after Mir landed that knee... but i think if him and Cain fight.. and Cain can use the same boxing skills he used on Noguiera.. i think he has a great chance against Lesnar.